Simulate drag and drop of SELECTED text

User selects some arbitrary portion from a block of text (or any portion of of a web page), the selection is then highlighted (in blue, I suppose. Not that it matters), then the user can drag the selected text and drop it (into a form field in my case.

I just want the user to be able to make the selection begin and end as they see fit. Rather than the whole block of text (or object) be dragged as one.